Exposure to cocaine decreases the proportion of AMPA receptors relative to NMDA receptors at PPN synapses by changing the NMDA receptor content. A, After a single exposure to cocaine in vivo, oPPN-evoked AMPA (red) receptor-mediated and NMDA (blue) receptor-mediated currents become similar to oSTN-evoked, oDR-evoked, and electrically evoked (Elec.; stimulus artifact removed) currents. The oPPN-evoked EPSC and electrically evoked EPSC were recorded from the same dopamine neuron. Total EPSC is indicated by the traces in black. B, Cocaine decreases the ratio of AMPA-to-NMDA currents at PPN inputs, but does not affect the AMPA-to-NMDA ratio of oSTN-evoked, oDR-evoked, or electrically evoked EPSCs. C, The amplitude of the AMPA receptor-mediated EPSCs evoked from oPPN, oSTN, and oDR, are not significantly affected after exposure to cocaine. D, Exposure to cocaine significantly increases the amplitude of NMDA receptor-mediated currents evoked by oPPN, but not oSTN or oDR. E, F, NMDA receptor-mediated EPSCs evoked by oPPN show a reduced rise time (E) and time constant of decay (F) after cocaine administration. *p < 0.05, **p < 0.01.